Soil forms when weathered parent material interacts with environment.

• Soil environment includes:
– Climate and weather
– Animals
– Microbes
– Human use
– Hazards ( natural and unnatural )
– Topographical relief

Slow--------------------------------------Fast
~ 1 cm/1000 yr ~ 30cm/50yr

• 1941: soil is open system, properties are functionally related; system changes when property(ies) change(s).
• Jenny’s CLORPT equation s = ƒ (cl, o, r, p, t)

1. CL IMATE
2. O RGANISMS
3. R ELIEF
4. P ARENT MATERIAL
5. T IME

CL
…determines speed, character of soil development: type and rate of weathering living organisms and plants found in an area

components of climate :
1. Temperature
-for every 10°C , biochemical rxn rates 2X
2. Effective precipitation
(water that moves through entire soil column, including regolith)
-depth of water = depth of weathering
-water moves soluble & suspended materials

• (Fig. 2.15)

-a) seasonal distribution
-b) temperature, evaporation
-c) topography
-d)permeability

a) Seasonal distribution of precipitation:
Location A
600 mm/yr
50mm
Location B
600 mm/yr
100mm
Every month 6 rainy months only

b) Temperature and evaporation:
Location A hot
High evapotranspiration
600 mm
Location B cool
Low evapotranspiration
600 mm
Lower effective ppt Higher effective ppt

Topography: level slope concave or bottom of slope
(receiving)

Permeability:

plant and animal
(Living plants and animals on and in soil)
-type of vegetation influences soil type
-base pumping
-sources of organic matter
-nutrient recycling
-vegetation prevents erosion

Type of vegetation influences soil type

Deciduous trees are more effective base pumpers than conifers .
-deciduous litter is easy to break down
-cations (bases) are released so surface soils are not acidic
-needles are hard to break down
-basic cations leach away: soil is acidic

• Macroanimals (insects, mammals, gastropods, earthworms)
– mix, bind soil; create channels for air, water

crotovinas

• Macroanimals (insects, mammals, gastropods, earthworms)
– mix, bind soil; create channels for air, water
• Microanimals (nematodes, protozoa)

• Macroanimals (insects, mammals, gastropods, earthworms)
– mix, bind soil; create channels for air, water
• Microanimals (nematodes, protozoa)
• Macroplants (the green plants)
– provide organic matter, roots create channels, adsorb nutrients, release CO stabilize, protect from erosion
2
,

• Macroanimals (insects, mammals, gastropods, earthworms)
– mix, bind soil; create channels for air, water
• Microanimals (nematodes, protozoa)
• Macroplants (the green plants)
– provide organic matter, roots create channels, adsorb nutrients, release CO stabilize, protect from erosion
2
,
• Micro “plants” (fungi, bacteria, actinomycetes, algae)
– decomposers

• important for rate of runoff, erosion, drainage

Flat valley floors and flat ridge tops: soil accumulates;
(deepening>removal)
Slopes : (removal> deepening)

• Vertical Zonation
– soils, climate, vegetation change with elevation

• Determines texture, types of weathering, mineral make-up

• Physical (Mechanical): disintegration of parent material; increases surface area:
– surface area increases by same factor as particle size decreases
• Chemical (Biogeochemical) : primary minerals are broken down and secondary minerals are formed

• Physical:
1. Freeze/thaw
2. Exfoliation
3. Abrasion
4. Salt wedging
• Chemical (biogeochemical):
1. Hydrolysis : minerals react with H
2
H + replace soluble parts; OH combine with mineral cations
O
2. Hydration : mineral combines with
H
2
O
3. Oxidation : mineral combines with O
2
(lose electron)
Reduction : loss of O
2
(gain electron)
4. Carbonation : oxides combine with acids to make carbonates
5. Complexation : organic acids form organic complexes with metal cations

• Physical:
1. Freeze/thaw
2. Exfoliation
3. Abrasion
4. Salt wedging
• Chemical (biogeochemical):
1. Hydrolysis : minerals react with H
2
H + replace soluble parts; OH combine with mineral cations
O
2. Hydration : mineral combines with
H
2
O
3. Oxidation : mineral combines with O
2
(lose electron)
Reduction : loss of O
2
(gain electron)
4. Carbonation : oxides combine with acids to make carbonates
5. Complexation : organic acids form organic complexes with metal cations

• Physical:
1. Freeze/thaw
2. Exfoliation
3. Abrasion
4. Salt wedging
• Chemical (biogeochemical):
1. Hydrolysis : minerals react with H
2
H + replace soluble parts; OH combine with mineral cations
O
2. Hydration : mineral combines with
H
2
O
3. Oxidation : mineral combines with O
2
(lose electron)
Reduction : loss of O
2
(gain electron)
4. Carbonation : oxides combine with acids to make carbonates
5. Complexation : organic acids form organic complexes with metal cations

wind

water

ice

• Physical:
1. Freeze/thaw
2. Exfoliation
3. Abrasion
4. Salt wedging
• Chemical (biogeochemical):
1. Hydrolysis : minerals react with H
2
H + replace soluble parts; OH combine with mineral cations
O
2. Hydration : mineral combines with
H
2
O
3. Oxidation : mineral combines with O
2
(lose electron)
Reduction : loss of O
2
(gain electron)
4. Carbonation : oxides combine with acids to make carbonates
5. Complexation : organic acids form organic complexes with metal cations

• Amount of time soil has been exposed to weathering and soil forming processes influences soil properties.
– Jenny’s staircase
– Ohio/Ky.

Transformation

Transformation
Translocation

Transformation
Translocation
Addition

Transformation
Translocation
Addition
Loss